1. Field of the Invention
The present invention relates to a locking device applicable to cash handling machines, for example, such as an automatic vending machine, a gaming machine, an automatic cash dispenser, a money exchanger and the like.
Conventionally, there are two known types of such locking device, one type being a pin tumbler having a reciprocating motion and the other being a disc tumbler having a sliding motion.
In the former type locking device, a plurality of pin tumblers are arranged longitudinally within an inner cylinder at equal intervals and a spring is interposed between the outer and inner cylinders to engage the upper portion of each pin tumbler to the outer cylinder and the lower portion to the inner cylinder. It is so arranged that, as a key is inserted into a key hole of the locking device, the lower portion of each pin tumbler retreats all together to the outer cylinder, thereby releasing the locked condition.
In such a lock construction, however, because a spring must be provided at each pin tumbler, it is not only troublesome to assemble, but the locking device itself is required have to be large because of the increased adjacent spaces between the pin tumblers. Thus the number of key settings is limited.
In the latter type locking device, it is so arranged that a plurality of disc tumblers are mounted in the inner cylinder and as each disc tumbler is slid by the set amount by the operation of the key, all the disc tumblers will be contained within the inner cylinder in alignment, thereby releasing the engagement with the notch in the outer cylinder and allowing the inner cylinder to rotate.
In such a lock construction, however, the strength of the disc tumbler is weakened by the key hole opened in the center of the plate thereof. Thus when a strong external force is applied to the disc tumbler engaging the outer cylinder, there is a possibility that the disc tumbler may be crushed and destroyed, resulting in a violently forcible unlocking.